Electronic band structure optical properties

The empirical approach [7] was by far the most fruitful first attempt. The idea was to fit a few Fourier coefficients or form factors of the potential. This approach assumed that the pseudopotential could be represented accurately with around three Fourier form factors for each element and that the potential contained both the electron-core and electron-electron interactions. The form factors were generally fit to optical properties. This approach, called the Empirical Pseudopotential Method (EPM), gave [7] extremely accurate energy band structures and wave functions, and applications were made to a large number of solids, especially semiconductors. [8] In fact, it is probably fair to say that the electronic band structure problem and optical properties in the visible and UV for the standard semiconductors was solved in the 1960s and 1970s by the EPM. Before the EPM, even the electronic structure of Si, which was and is the prototype semiconductor, was only partially known. 

Quantum size effects in semiconductor nanocrystals became an important field of research in the 1980s, when a number of groups, notably those of Brus at Bell Labs and Henglein at the Hahn Meitner Institute, published seminal papers on the effects of the size of semiconductor colloids on their optical properties and correlated crystal size with changes in electronic band structure. 

Conjugated conducting polymers consist of a backbone of resonance-stabilized aromatic molecules. Most frequently, the charged and typically planar oxidized form possesses a delocalized -electron band structure and is doped with counteranions (p-doping). The band gap (defined as the onset of the tt-tt transition) between the valence band and the conduction band is considered responsible for the intrinsic optical properties. Investigations of the mechanism have revealed that the charge transport is based on the formation of radical cations delocalized over several monomer units, called polarons [27]. 

Painter, G. S. and J. E. Ellis. 1970. Electronic band structure and optical properties of graphite from a variational approach. Phys. Rev. B 1 4747-4752. 

As will be shown in the following sections the results of the one-electron band structure calculations allow to describe several important properties of the tetracyanoplatinates, like the dominance of the Pt 5 dz2 and Pt 6 p2 orbitals for the red-shift of the main optical transitions with decreasing metal-metal distance82 6, the admixture of Pt(6pz, CNji ) character into the valence band82,89, or several stabilization effects upon partial oxidation84. On the other hand, a series of experimentally found features is out of the scope of the one-electron band model. In the following some of these properties are specified ... 

The electronic properties of binary and ternary intermetallic Zintl phases crystallizing in the NaTl type of structure are investigated and reported. The crystal and defect structure, the electronic band structure and density of states, the bonding mechanisms and the charge transfer are discussed. Comparison is made between the electronic states in the B2 and the B32 types of structure. Furthermore, based upon theoretical studies of the electronic valence states the optical properties (imaginary part of the dielectric constant and reflectivity) and the magnetic properties (susceptibility and Knight shift) are considered. 

Optical Properties of Polythiophenes Electronic Band Structure and UV-Visible Spectra... 

Conjugated polymers have an electronic band structure. The energy gap (Eg) between the highest occupied n electron band (valence band) and the lowest unoccupied one (conduction band) determines the intrinsic optical properties of the polymers. 

Dimmock, J.O., A.J. Freeman, and R.E. Watson, 1966, Electronic band structure and optical properties of rare earth metals, Abeles, F. ed.. Proceedings of the International Colloquium on Optical Properties and Electronic Structure of Metals and Alloys, Paris, 1965, (North-Holiand Publishing Co., Amsterdam), pp. 273-245. 

Potter et al. (1992) reviewed the literature on the microstructure of semiconductors in a composite structure with an insulating matrix. These composites offer insight into the electronic band structure and the optical properties of the materials. Simmons et al. (1991) discussed the electronic band structure of composites formed from semiconductors and glass components. 

A chapter introducing the Bose-Einstein, Maxwell-Boltzman, Planck, and Fermi-Dirac distribution fimctions follows before discussing the thermal, electronic, magnetic, and optical properties for the benefit of students who have not been exposed to quantum statistical mechanics. This chapter is a logical beginning for the second half of this book since these concepts are essential to an imderstanding of these properties. Similarly, the Maxwell equations are used to derive the equations for absorption and normal reflection of electromagnetic waves in the chapter on optical properties. The band structure of metals... 

The electrical and optical properties of semiconductors are mainly governed by the electronic band structure (BBS) in the vicinity of the absolute VB... 

Palladium Ensembles in Zeolites. Small metal particles or clusters have attracted great interest during the last decade. The optical, electronic and catalytic characteristics of clusters are expected to change from bulk properties to molecular properties within a certain size-range. " This change is represented by the transition of the electronic band structure of a crystal to the molecular orbital levels of species few atoms in size. Since the cluster size determines the relative population of coordination sites and possibly its molecular symmetry, it is thought to be responsible for modified selectivities in a number of catalytic reactions. Controlled synthesis of stable clusters with defined size is of particular interest, because this would potentially allow to fine-tune the properties of electronic materials and catalyst systems. 

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